In typora, you could just press $$ and Return key to input a math block, in input mode, use Up/Down arrow key or Command/Ctrl + Renturn key to finish editing, or just click the ✓ button, or somewhere else.

Inline Math

First of all, please enable inline math feature from preferences panels -> Markdown section. Preferences panel can be opened From menu bar: File -> Preferences..., or use shortcut key — command/ctrl + ,. This settings will be applied after Typora restarts.